It is the dead of winter in the Northern Hemisphere, the Hummingbirds have gone south, and we’re writing — again — about how to count them. For northerners, it’s for future reference. The planet is tilting, spring will return, and so will the hummingbirds.
Last August we published a method of estimating the number of Hummingbirds you feed based on the amount of nectar disappearing from your feeders. You can read that post here. The method we suggested came from a book about hummingbirds by Dan True who, in turn, based his methodology on a 1973 scientific study.
With appropriate humility, given that we are not professional ornithologists or even biologists, we noted that if the 1973 study was wrong, the methodology might be as well. We invited readers to weigh in on the subject.
Last week someone did. A professional. One who has written a book about hummingbirds. A professional who assures us the 1973 study was wrong and that Dan True’s book is, “full of half-baked ideas, misinterpretations of other people’s work, and out-of-date information such as the sugar-consumption figure on which the TFFBB bloggers based their feeder-usage formula.”
With our out-dated, clumsy method; using wrong data ,we told you that 8 ounces of sugar solution was probably feeding about 25 hummingbirds each weighing 5 ounces. Our correspondent, using modern scientific data, says 8 ounces of sugar water feeds about 32 hummingbirds each weighing 3.5 ounces. In other words, our half-baked method came up with almost precisely the same answer as modern fully-baked science. Still, it is better to be right for the right reason than right for the wrong reason.
Reduced to essentials, our reader’s method consists of assuming that each bird eats about 1/4th of an ounce of solution a day. (Her entire explanation is here.) An ounce feeds four birds, 8 ounces feeds 32 birds. You must, of course, adjust for the amount of time it takes to drain the feeder. If it takes one-half a day to empty, then you have 64 birds. If it takes two days to empty, you have 16. (If it takes longer than two days for the birds to empty the feeder, you need to put fresh solution in it. Just sugar and water. No food coloring.)
This is, as she says, only a “crude” estimate since it assumes uniformly sized 3.5 oz. birds, does not include other food sources, stress, mating, and migration needs. (The need to fatten for migration was the reason we used an average weight of 5 ounces per bird in our August calculation.)
She also refers to another method of counting. Count the number of hummingbirds at your feeder at a given moment in time and multiply by six. She doesn’t endorse that method and neither do we since we’ve never tried it. It has the attraction of simplicity but lacks scientific rigor, a matter to which we return in the next post.
For you see, modern fully-baked science can’t tell for sure how many hummingbirds you are feeding. All it can do is make a “crude” estimate. It can’t even tell us with any certainty how Ruby-throated Hummingbirds (“Colibri Garganta de Rubi”, down there.) make their way to and from Central America. We’ll have more to say about that next time.
That is an angelic Black-chinned Hummingbird in the photo at our Schrodt feeder last summer.